Self-aligning plunger drive



2 sheets-sheet 1 Filed Nov. 26, 1954 Hlli July 22, 1958 R. A. BENNETT2,844,103

' SELF-ALIGNING PLUNGER DRIVE Filed Nov. 26, 1954 2 Sheets-Sheet ,2

United States Patent SELF-ALIGNING PLUNGER DRIVE Richard Allen Bennett,Elkins Park, Pa., assignor to Milton Roy Company, Philadelphia, Pin, acorporation of Pennsylvania This invention relates to controlled volumepumps, more particularly to pumps of the submersible type adapted tometer or to produce an accurately controlled flow of liquid from a tankcar, a storage tank, or a vat, or from a small vessel.

In the development of a submersible type of pump meeting therequirements of a highly accurate metered flow of a liquid, and asdisclosed by copending application Serial No. 465,307, filed October 28,1954 by Royal Bartlett Saalfrank, a co-employee of mine, something wasleft to be desired in providing longer trouble-free operation byavoidance of eventual scoring and damage to the packing surrounding theplunger.

A purpose of the invention is to avoid or minimize scoring of packing,or of the plunger or the cylinder when a piston is actuated in acylinder by reciprocatingmeans such as a push rod which extendsgenerally axially but which may not be truly axial in motion throughoutits entire stroke.

A further purpose is effectively to pull the plunger through thecylinder on the pressure stroke by application of the force to theplunger within 25 percent of the distance from the forward end of theplunger to the outside end of the packing so as to minimize thereon a"lateral component of the actuating force on the plunger.

A further purpose is to provide a plunger rod extending through theinterior of the plunger and having a laterally shiftable connectionbetween the plunger rod and the plunger to compensate for motion of theplunger rod in a direction slightly deviating from the axial directionalong the stroke.

In carrying out the present invention in a preferred form thereof, anelongated plunger which is moved into and out of a plunger chamber hasthe actuating force on the pressure stroke applied thereto at a regionin close proximity to its forward end. By reason of this provision, theeffect on the plunger as a whole is a selfcentering one, analogous andequivalent to an idealized arrangement in which the plunger would beactuated by pulling it from its forward end to produce the pressure orworking stroke. A similar action is likewise produced on the returnstroke, the point of application of the actuating force shifting witheach stroke from the leading to the trailing end of the plunger.

For a more complete understanding of the invention and for furtherobjects and advantages thereof, reference is to be had to the followingdescription taken in conjunction with the accompanying drawings, inwhich:

Fig. l is a side elevation, partly in section, of the pump of saidcopending application with the present invention applied thereto; and

Fig. 2 is an enlarged sectional elevation of the lower part of Fig. 1.

In many pump applications, especially in deep well pumps and sump pumps,it is desirable to apply the actuating force to a piston in a pumpcylinder by reciprocating motion, applied, for example, through a icepush rod which moves generally axially. This presents problems which arenot usually encountered in an ordinary pump installation where theplunger or piston is driven by a connecting rod from a crank oreccentric. There arises a tendency for the reciprocating element, suchas the push rod, to deviate from the truly axial direction at some pointalong its course of travel. This tendency is particularly pronouncedwhere the structure is elongated, and where, for example, it is possiblefor shift of relative position to take place even after installation ofthe equipment, for example, due to deflection of the supporting parts.

While variations from the axial path are objectionable even in pumpswhich are not intended for precision pumping, this device isparticularly objectionable in metering pumps which should deliverprecisely measured quantities of liquid within an accuracy of, forexample, 1 percent or a few percent. Here deviation from axiality islikely to result in scoring of the packing, the cylinder or the pistonor some combination of the same, with the result that changes in thevolume relationships and/or leakage may occur, and the pump will ceaseto deliver accurately.

The present invention is designed to produce highly accurate delivery ofliquid to be pumped even in a submersion pump or other structure wherethe actuation is accomplished by a reciprocating member, and especiallywhere the reciprocating member is elongated and likely to deviate fromtrue axial relationship.

In accordance with the invention, the driving force is applied to aplunger near the front on the pressure stroke so that instead of beingpushed, the plunger is in effect pulled. This in itself reduces thetendency to create a lateral component on the plunger due to deflectionor deviation from axiality which would cause scoring. In the preferredembodiment, the force is applied. to the plunger in the forward 15percent of the plunger length, measuring from the forward end of theplunger to the outside end .of the packing at full stroke. This assuresthat the greater part of the length of the plunger, and particularly thepart that is traveling through the packing, will be in a trailingposition with respect to the force application, thus greatly reducingthe tendency to score.

The invention furthermore contemplates that there will be lateralfreedom between the plunger and the reciprocating force-applying member,generally referred to as a plunger rod, so that instead of distortingthe plunger rod where the motion of the push rod is not axial, therelative position of the plunger rod and the plunger can shift slightlylaterally without applying any radial or lateral force component ofappreciable magnitude on the plunger.

Referring now to the drawings, the invention in one form has been shownas applied to a pump of the submersible type as disclosed in saidcopending Saalfrank application, and in which a motor 10 through astrokeadjusting mechanism 11 and an actuating member 12 moves anelongated plunger 26, Fig. 2, within the cylinder or plunger chamber 27of a combined valve and cylinder block 13. The driving connection fromthe stroke-adjusting mechanism 11, Fig. 1, is by way of a link 14 and arod 15 guided in a bracket 16. The rod 15 is connected to a tubularmember 17 which has its lower end secured to an upper driving member 18.Preferably three drive rods, two of which, the rods 19 and 20 appear inthe drawing, interconnect the upper driving member 18 and a lowerdriving member 21. The three rods are spaced apart and areguide-supported in openings in the cylinder block 13.

As best shown in Fig. 2, there is a floating driving connection betweenthe cross-head or lower driving member 21 and the plunger-rod oractuating member 12. The driving connection is formed by an enlargedhead 23 secured as by a pin 24 to the plunger actuator 12. The enlargedhead 23 has freedom of movement in all radial directions in a recessclosed by a lock nut 25, the lower end of which forms an upper bearingsurface for the enlarged head 23.

The plunger 26 is counterbored to a point adjacent its upper end toreceive within the elongated opening the enlarged upper portion 12a ofactuator 12. The lower portion of the actuator 12 of smallercross-sectional area extends loosely through a member 29 which is itselfthreaded into the lower end of the plunger 26. Thus, as will be seen,the member 29 effectively forms a part of plunger 26 and particularlywith respect to its cooperative relationship with the lower surface ofthe enlarged portion 12a. The distance between the upper face of themember 29 and the upper wall of plunger 26 is slightly greater than thelength of the enlarged portion 12a of actuator 12, leaving, with theparts in the position illustrated, a slight axial clearance between thelower face of the enlarged portion 12a and the upper face of the member29.

With the parts in the position shown, the forward or pressure stroke hasjust been completed and the upper face of the plunger-actuator 12 isshown bearing against the surface 26a of plunger 26. All portions ofplunger 26 below the surface 26a have applied thereto tensional forcesand thus the forces tending to move the plunger upwardly are the same asthough the plunger were drawn upwardly by pulling from the upper endthereof. By reason of the foregoing arrangement, there is little, ifany, tendency of the plunger to be tilted within the cylinder 27.

In this connection, it is to be noted that in a metering or controlledvolume type of pump the plunger 26 loosely fits within the plungerchamber or cylinder 27. The metered flow of liquid arises from thevolumetric displacement thereof by the plunger 26 and not by reason of aliquid-tight seal between the adjacent surfaces of the plunger andcylinder.

As the return stroke is initiated, there is a slight movement ofplunger-actuator 12 downwardly to bring the surface of the shoulderformed by the lower face of the enlarged portion 12a against the upperface of the threaded member 29. Upon engagement of said surfaces,downward movement of plunger 26 is initiated. The downward movement isproduced by surfaces located adjacent the lower end of the plunger 26.Thus,

on the return stroke the tensional or pulling forces are applied to thelower end of the plunger, minimizing any tendency for it to be tilted orcocked within the cylinder 27. As the plunger 26 descends, liquid entersthe cylinder by way of an inlet 31 provided in a ball valve assembly 32.The balls 32a and 32b thereof rise to open the passageway for flow ofliquid by way of channel 34 into the cylinder which at all times remainsfull of liquid. Upon completion of the suction or downward stroke of theplunger 26, the ball valves close.

Upon upward movement of plunger 26, the resultant pressure is applied toa valve assembly 35 having balls 35a and 35b which are thereupon movedto their illustrated positions to open the vertically extendingpassageway into the outlet pipe 36 for outward flow of liquidtherethrough. It is to be observed that there is lacking any possibilityof air entrapment within the system since the passageway 34 has anentrance into the cylinder adjacent the uppermost part thereof.

Though other packing means may be utilized, I prefer to use a spring 38disposed with its upper end against a shoulder formed in a counterboreof the cylinder block 13, the spring at its lower end bearing againet ametal ring 39 to apply spring pressure against packing elements 40 heldin place by a threaded gland member 41.

By reason of the fact that there is a transfer of the point ofapplication of the actuating force to the plunger 26 first from thedriving connection at one end thereof and then to the driving connectionat the opposite end thereof upon each reversal of movement, there isavoided or minimized to a negligible degree any tendency of the plunger26 to be tilted or cocked and to dig into or otherwise score or injurethe inner surfaces of the packing elements 40. By providing clearancebetween the enlarged upper portion 12a of actuating member 12 and theinner bore of the plunger 26, there is alwayspresent a seif-centeringaction. The member 12 may bodily move radially or laterally of theplunger 26. The plunger 26 is driven upwardly in coaxial alignment withthe actuating member 12 and its enlarged portion 12a. The self-aligningaction maintains plunger 26 coaxial of the cylinder or plunger chamber27. The degree to which the self-centering action is effective has beendemonstrated to be sufficient materially to extend the useful life ofthe packing elements 40 and to provide longer runs between servicing andrenewal of such packing elements.

As shown in the drawings, the respective ends of the enlarged portion12a of the actuating member are located quite close to the ends of theplunger 26. Instead of having the actuating force applied at the lowerend of plunger 26, the actuating force on the upward or pressure strokeof plunger 26 is applied at a point near the upper end which is removedfrom the upper face thereof by only 10 percent to 15 percent of thetotal length of the plunger 26. While it is preferred that the force ofthe upper face of actuating member 12 be applied on the working strokeas near the upper face of plunger 26 as possible, improved results willbe obtained if the points of engagement are respectively displaced fromthe upper and lower faces by as much as 25 percent.

By reason of the lateral freedom between the head of the actuatingmember or plunger rod 12 and the piston, the piston can shift slightlylaterally in case the plunger red head 21 does not move on the axialcourse. It will be evident that these lateral adjustments may be in therealm of micro inches in some cases, and in the realm of thousandths ofan inch in other cases but their effect is substantial as they permitthe piston to travel on the compression stroke particularly, and also onthe suction stroke, with minimum or no lateral component of movement.

It will be evident that these features are important out of allproportion to the cost of replacing the packing, the piston or thecylinder due to the fact that the location of the pump, due toinaccessibility, hazardous nature of the surrounding area, or the likemay not permit inspection, so that if the parts seriously wear or score,the pump may fail to meter accurately and thus cause serious errors inchemical reaction or in the metered flow of liquids whose quantity mustbe accurately controlled, without the possibility of knowledge by theoperator.

It is to be understood the present invention can be applied to otherforms of pumps and that I have explained it in connection with themechanism disclosed in said Saalfrank application in order to show thetype of pump in which the invention has proven to be entirelysatisfactory.

What is claimed is:

1. In a controlled volume pump, the combination of a cylinder blockhaving an elongated plunger chamber open at one end thereof and closedat a discharge end thereof, inlet and outlet valves in how communicationwith said discharge end of said chamber, an elongated hollow plungerclosed at one end and open it its opposite end disposed forreciprocation between a position substantially filling said chamber to aposition largely withdrawn from said chamber, stationary packing meansfor said plunger forming a liquid seal between said plunger and thatportion of said chamber adjacent said open end, driving means forreciprocating said plunger free from development of radial forces ofsubstantial magnitude comprising an elongated actuating element disposedwithin said hollow plunger, said plunger and said actuating element eachhaving driving surfaces located at opposite end portions of saidelongated plunger, the distance between said surfaces on said actuatingelement being less than between said surfaces on said plunger foralternate engagement of said surfaces at said opposite end portions ofsaid plunger, said actuating element vextending outwardly of said hollowplunger through the open end thereof and having radial clearancetherewith for relative radial movement between said plunger and saidelement, and reciprocating means connected to said outwardly extendingactuating element for moving said element to engage said drivingsurfaces located adjacent the closed end of said plunger for moving saidplunger into said chamber and for moving said element to disengage saidlast-named surfaces and to engage said driving surfaces adjacent saidopen end of said plunger for moving said plunger outwardly of saidplunger chamber.

2. In a controlled volume pump, the combination of a cylinder blockhaving an elongated plunger chamber open at one end thereof and closedat 'a discharge end thereof, inlet'and outlet valves in flowcommunication with said discharge end of said chamber, an elongatedhollow plunger closed at one end and open at its opposite end disposedfor reciprocation between a position substantially filling said chamberto a position largely Withdrawn from said chamber, stationary packingmeans adjacent the open end of said plunger chamber forming a liquidseal between said plunger and the wall of said chamber, driving meansfor moving said plunger axially of said plunger chamber free fromdevelopment of radial forces of substantial magnitude comprising anelongated actuating element disposed within said hollow plunger, saidplunger and said actuating element each having driving surfaces locatedat opposite end portions of said plunger, the distance between saidsurfaces on said element being less than between said surfaces on saidplunger for alternate engagement of said surfaces at said opposite endportions of said plunger, said actuating element extending outwardly ofsaid hollow plunger through the open endthereof and having radialclearance therewith for selfcentering relative radial movement betweensaid plunger and said element, and reciprocating means including amember connected to said outwardly extending actuating element andextending outwardly beyond the cylinder block of said chamber, and rodmeans connected to said member and extending in spaced relation withsaid cylinder block in the region of said plunger chamber to a positionin spaced relation with said valves for moving said element to engagesaid driving surfaces located adjacent the closed end of said plungerfor moving said plunger into said chamber and for moving said element todisengage said last-named surfaces and to engage said driving surfacesadjacent said open end of said plunger for moving said plunger outwardlyof said plunger chamber.

3. In a controlled volume pump of the submersible type, the combinationof a cylinder block having an elongated plunger chamber open at thelower end thereof and closed at its upper discharge end thereof, inletand outlet valves in flow communication with said discharge end of saidchamber, an elongated hollow plunger closed at one end and open at itsopposite end disposed for reciprocation between a position substantiallyfilling said chamber to a position largely withdrawn from said chamber,packing means for said plunger forming a liquid seal between saidplunger and said open end of said chamber, driving means forreciprocating said plunger free from development of radial forces ofsubstantial magnitude comprising an elongated actuating element disposedwithin said hollow plunger, said plunger and said actuating element eachhaving driving surfaces located at opposite end portions of saidplunger, the distance between said surfaces on said element being lessthan between said surfaces on said plunger for alternate engagement ofsaid surfaces at said opposite end portions of said plunger, saidactuating element extending downwardly from and outwardly of said hollowplunger through the open end thereof and having radial clearancetherewith for relative radial movement between said plunger and saidelement, a lower driving member, an upper driving member, rod meansrigidly interconnecting said members, a mechanical connection betweensaid lower driving member and the lower end of said actuating elementhaving radial clearance for relative radial movement between said lowermember and said element, reciprocating drive means disposed above saidplunger chamber having a drive rod extending downwardly therefrom, and amechanical connection between said upper driving member and said driverod having radial clearance for relative radial movement between themfor moving said element to engage said driving surfaces located adjacentthe closed end of said plunger for moving said plunger into said chamberand for moving said element to disengagesaid last-named surfaces and toengage said driving surfaces adjacent said open end of said plunger formoving said plunger outwardly of said plunger chamber.

4. In a controlled volume pump including a plunger chamber, inlet andoutlet valve means connected to the interior of the plunger chamber, anelongated plunger movable into and outwardly of the plunger chamber, andreciprocating means moving longitudinally and axially of the plungerchamber for reciprocating the plunger, the improvement which comprisesan elongated driving element connected to the reciprocating meansextending into and surrounded by the plunger, and laterally shiftabledriving connections between said plunger and said driving elementrespectively located adjacent opposite end portions of said elongatedplunger and selectively effective to move said plunger, relative axialmovement of said driving elementrelative to said plunger uponreciprocation of said driving element rendering effective first one andthen the other of said driving connections for movement of said plungerby the driving connection adjacent the end portion of said plunger whichforms the leading end thereof during its movement into and out of saidplunger chamber.

References Cited in the file of this patent UNITED STATES PATENTS850,583 Howard Apr. 16, 1907 1,254,784 Esnault-Pelterie Jan. 29, 19182,130,037 Skarlund Sept. 13, 1938 2,436,908 Van Weenen Mar. 2, 1948

